Method of manufacture of a structural body

ABSTRACT

The rotary tools are disposed to weld along two spaced welding lines. The two rotary tools are inserted into respective welding joints and moved at the same time along the respective welding lines. At a position P 1  of a portion of a window one rotary tool is withdrawn from the welding joint so that the friction stir welding on that welding joint is stopped although the welding tool continues to move. At a position P 3,  the rotary tools are gradually withdrawn from their respective welding joints while they continue to move along the welding line. At a position P 4,  the movement of the rotary tools along the respective welding lines is stopped, the rotary tools are completely withdrawn and the welding is stopped. Next, the rotary tools are inserted into the respective welding joints once again and movement thereof is started again. An insertion amount of the rotary tools at this time is larger than the insertion amount thereof prior to the stopping of the movement of these rotary tools.

This is a divisional application of U.S. Ser. No. 09/572,985, filed May17, 2000 now U.S. Pat. No. 6,273,323.

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a structuralbody using a friction stir welding method; and, for example, theinvention relates to a manufacturing method suitable for the manufactureof a car body of a railway vehicle

Friction stir welding is a method wherein a round rod (called a “rotarytool”), which is inserted into a welding joint, is rotated and movedalong the welding joint so that the welding joint is heated, softenedand solid-fluidized, whereby a solid phase welding occurs.

The rotary tool comprises a small diameter portion which is insertedinto the welding joint, and a large diameter portion which is positionedoutside of the small diameter portion. The small diameter portion andthe large diameter portion of the rotary tool have the same axis ofrotation. A boundary between the small diameter portion and the largediameter portion of the rotary tool is inserted slightly into thewelding joint. The rotary tool is inclined toward the rear relative tothe advancing direction of the welding.

A car body of a railway vehicle is constituted by carrying out afriction stir welding of plural extruded frame members. The longitudinaldirection of the extruded frame member is directed in the longitudinaldirection of the car body, and the width of the extruded frame member isarranged in the direction of the height of the car body. To a side faceof the car body with the above-stated construction, an opening, such asa door or window, is typically provided by cutting-out a portion of theextruded members.

The above-stated technique is disclosed in Japanese application patentlaid-open publication No. 09-309164 (EP 0797043A2).

Since the height of a window of a car body is typically larger than thewidth of an extruded frame member, the window is formed by an openingcut into two or three frame members. For this reason, the extruded framemembers in which a cut-off portion is provided are substantially alignedto form the window and then joined by welding. A friction stir weldingapparatus for manufacturing a car body comprises a bed for mountingplural extruded frame members and a gantry disposed over the bed andfrom which plural rotary tools are suspended. By controlled movement ofthe gantry, the plural rotary tools are moved so that plural extrudedframe members can be welded simultaneously.

In a case where the plural extruded frame members are weldedsimultaneously using plural rotary tools which are suspended from agantry, when a first rotary tool reaches a position where a window islocated, this rotary tool is withdrawn from the extruded frame member,and the friction stir welding being performed by this rotary tool isstopped. Meanwhile, a second rotary tool for welding a portion where awindow does not exist is allowed to continue the friction stir weldingas it is. When the first rotary tool is moved to a position at the otherend of the window, this first rotary tool is inserted once again intothe weld joint and the friction stir welding is resumed.

When this process is carried out, by removing the first rotary tool fromthe welding joint at one side of the window and then re-inserting intothe welding joint at the other side of the window, a defect in thewelding can be generated easily. Further, at an initial time during thestart of the friction stir welding since the temperature of the weldingjoint has not yet been raised, a large insertion force is required forinserting the rotary tool into the welding joint.

In addition to the above, since the rotary tool is moved while it isinserted into the welding joint, a slant force is generated against abearing member of the rotary tool. For this reason, the bearing memberis required to be large in size, and a problem with the life expectancyof the rotary tool occurs.

SUMMARY OF THE INVENTION

A first object of the present invention is to obtain good friction stirwelding in a case of welding plural lines simultaneously, while aportion of the member or members to be subjected to welding does notexist or in which friction stir welding is unnecessary, when thefriction stir welding begins again after being interrupted.

A second object of the present invention is to perform friction stirwelding in a short time in a case of welding plural linessimultaneously, where a portion of the member or members to be subjectedto welding does not exist or in which friction stir welding isunnecessary.

The above-stated first object can be attained by a method ofmanufacturing a structural body comprising the steps of: starting afriction stir welding by inserting respective rotary tools into pluralwelding joints at a first position; stopping the friction stir weldingof one welded joint by withdrawing one of the rotary tools from thatwelding joint, while continuing movement of the one of the rotary toolsaccompanying movement of the other of the rotary tools at a secondposition; stopping the movement of the respective rotary tools andstopping the friction stir welding while withdrawing the other of therotary tools from its welding joint; inserting the respective rotarytools to a predetermined depth into each respective welding joint; andstarting the friction stir welding by again starting the movement of therespective rotary tools along their respective welding joints.

The above-stated second object can be attained by a method ofmanufacturing a structural body comprising the steps of: startingfriction stir welding by inserting respective rotary tools into pluralwelding joints at a first position; withdrawing one of the rotary toolsfrom a welding joint, while continuing movement thereof accompanyingmovement of others of the rotary tools at a second position; and theninserting the one of the rotary tools into its welding joint once again.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing a method of manufacture of a structural bodyrepresenting one embodiment according to the present invention;

FIG. 2 is a flowchart showing a method of manufacturing a structuralbody according to the present invention;

FIG. 3 is a longitudinal cross-sectional view showing a structural bodyaccording to the present invention;

FIG. 4 is a perspective view showing a friction stir welding apparatusfor manufacturing a structural body according to the present invention;

FIG. 5 is a perspective view showing a car body of a railway vehicleaccording to the present invention; and

FIG. 6 is a diagram showing a method of manufacture of a structural bodyrepresenting another embodiment according to the present invention.

DESCRIPTION OF THE INVENTION

One embodiment of a method of manufacture of a structural body accordingto the present invention will be explained with reference to FIG. 1 toFIG. 5. As a structural body, a railway car body will be referred to byway of example. As shown in FIG. 5, the car body comprises a sidestructure 201 for constituting a side face of the car, a roof structure202 for constituting a roof of the car, a bogie frame 203 forconstituting a floor of the car, and an end structure 204 forconstituting an end of the car body.

The side structure 201, the roof structure 202, and the bogie frame 203are constituted respectively by joining plural extruded frame members.The longitudinal direction of each of the extruded frame member isdirected in the longitudinal direction of the car body. The material ofthe extruded frame member is an aluminum alloy.

As shown in FIG. 5, the side structure 201 comprises extruded framemembers 10, 20, 30 and 40. In the extruded frame members 20 and 30, awindow opening 210 is provided by cutting away parts of the framemembers 20, 30. An inlet and outlet port (doorway) 220 of the sidestructure 201 is provided by cutting away parts of the extruded framemembers 10, 20, 30 and 40. As to the inlet and outlet port 220, afterthe extruded frame members 10, 20, 30 and 40 have been joined, in manycases a frame is welded in position. The window 210 is formed in asimilar way. The extruded frame members 10, 20 and 30 of the inlet andoutlet port 220 are cut off at a respective midway portion.

This side structure 201 is comprised of the four extruded frame members10,20, 30 and 40, however, in a case of a hollow extruded frame member,the side structure 201 may be constituted by many more extruded framemembers. Further, it is possible for the window 210 to be constituted bythree extruded frame members. In this case, a central extruded framemember is cut off at a midway portion.

The construction of the extruded frame members used to form the sidestructure 201 will be explained with reference to FIG. 3. Herein, thejoining of the extruded frame members 20 and 30 will be explained. Theother frame members 10 and 40 are similar in configuration to theseextruded frame members 20 and 30. The extruded frame members 20 and 30are hollow frame members.

The hollow frame member 20 comprises two face plates 21 and 22, pluralribs 23 arranged in a truss shape for connecting the face plates 21 and22, and a supporting plate 24 for connecting the two face plates 21 and22 in an end portion (a joining portion) in a width direction of thehollow frame member 20. The hollow frame member 30 comprises two faceplate 31 and 32, plural ribs 33 arranged in a truss shape for connectingthe face plates 31 and 32, and a supporting plate 34 for connecting thetwo face plates 31 and 32 in an end portion (a joining portion) in awidth direction of the hollow frame member 30.

In the width direction of the end portion (the joining portion) of theface plates 21 and 22, a raised portion 25 projecting toward the outsideof the respective face plate is provided. In the width direction of theend portion (the joining portion) of the face plates 31 and 32, a raisedportion 35 projecting toward then outside of the respective face plateis provided. At the end portion in the width direction of the hollowframe member 30, a pair of projection chips 36 projecting toward theopposite hollow end of the frame member 20 are provided. The projectionchips 36 are located between the face plates 21 and 22 at the endportion of the face plates 21 and 22 of the hollow frame member 20 so asto form a seat for supporting the insertion force of a rotary tool 340.

The width of the two raised portion 25 are the same, and an end face ofthe raised portion 35 which bears against the raised portion 25 isarranged to extend substantially along the center of the plate thicknessof the supporting plate 34. At a center of the surface formed by the tworaised portions 25 and 35, i.e., where the welding joint is located, therotation axial center of the rotary tool 340 of the friction stirjoining apparatus 330 is positioned.

As seen in FIG. 4, the extruded frame members 10, 20, 30 and 40constituting the side structure 201 are mounted on a bed 310 of thefriction stir welding equipment 300 and are fixed to the bed 310 bysuitable means. Above the plural extruded frame members 10, 20, 30 and40 a gantry 320 runs on rails 329 located on both sides of the bed 310.From a girder 321 of the gantry 320, three friction stir weldingapparatuses 330 are suspended.

The friction stir welding apparatuses 330 operate to raise and lower therotary tools 340 for welding the frame members positioned on the bed310. The bed may be arc shaped. The respective friction stir weldingapparatuses 330 can be independently moved along the girder 321 to awelding position, at which the rotary tools 340 can be independentlyraised and lowered while rotating to effect selective welding.

The respective friction stir welding apparatuses 330 are provided withan optical sensor which detects the distance from the apexes of theraised portions 25 and 35 and sets an insertion amount of the rotarytool 340 at a predetermined value. Further, the optical sensors detectwidth of the surface formed by the raised portions 25 and 35 anddetermines a center thereof to position the axial center of the rotarytool 340 for welding.

In the extruded frame members 20 and 30 on which a window 210 isprovided, an opening (a cut-off portion) having substantially a windowshape is provided at the position of the window in advance. This openingis provided by cutting out a portion of the extruded frame members 20and 30. Similarly, the extruded frame members 10, 20 and 30 in which theinlet and outlet port 220 is provided are cut off and are arranged toaccommodate the interval of the inlet and outlet port 220. In theextruded frame member 40 for constituting an upper end of the inlet andoutlet port 220, an opening (a cut-off portion) having a substantiallyinlet and outlet port shape is provided at a position of the inlet andoutlet port 220 in advance. This opening is provided by cutting out aportion of the extruded frame member 40.

The formation of the window 210 will be explained. The welding joint ofthe extruded frame members 20 and 30 has a welding line having a startend and a finish end in the window 210. For this reason, as seen in FIG.1, the extruded frame members 20 and 30 in a vicinity of the weldingline are cut off while leaving the extending portions 28, 38 and 29, 39which project into the window 210. The width of the respective extendingportions 28, 38 and 29, 39 is set to have the same dimension as thesupporting plates 24 and 34 and the raised portions 25 and 35. Theformation of the inlet and outlet port 220 is carried out similarly. Theextruded frame members 10, 20, 30 and 40 are cut off while leavingrespective extending portions 28, 38 and 29, 39. Further, the extendingmembers chips 28, 38 and 29, 39 are provided respectively on both endsin the longitudinal 10 direction of the side structure 201.

The hollow frame members 10, 20, 30 and 40 are mounted on and fixed tothe bed 310 using a fixing means. When the hollow frame members 10, 20,30 and 40 have been fixed, the raised portions 25 and 35 of the abuttingportions of the hollow frame members 10, 20, 30 and 40 are fixedintermittently and temporarily along the welding lines by arc welding.The extreme ends of the extending portions 28, 38, 29 and 39 at thestart end and the finish end of the welding line are also fixedtemporarily.

A reference “W” in FIG. 1 shows where the temporary welding occurs. Inparticular, the temporary welding W of the start end is carried out onupper faces of the raised portions 25 and 35 and on a face of theextreme end portion in the longitudinal direction of the hollow framemembers 10, 20, 30, and 40. The range of the temporary welding “W”, onthe face of the extreme end portion is from the upper faces of theraised portions 25 and 35 to the projection chip 36. The temporarywelding “W” does not provide a V-shaped groove, but provides an I-shapedgroove.

In this condition, from one end in the longitudinal direction of thehollow frame member, the friction stir welding is started. To the raisedportions 25 and 35 of these chips at the starting end of the weldingline, by rotating the respective rotary tools 340, a rotary tool 340 isselectively lowered and inserted into the welding joint. The insertionposition is located at the finish end of the welding line on the otherside of the temporary welding W location at the end portion of the chip.For example, the insertion position is a position P4 of the rotary tool340A as shown in FIG. 1.

The chip end of the small diameter portion 341 of the rotary tool 340 isinserted into an upper face of the surface formed by raised portions 25,35 to the depth of the projection chip 36. The position to which thelowest end of the large diameter portion 342 of the rotary tool 340 isinserted is between the plane of the outer faces of the face plates 21and 31 (the face plates 22 and 32) and an apex of the raised portions 25and 35. The position of the axial center of the rotary tool 340 ismidway between the sides of the two raised portions 25 and 35. The axialcenters of the small diameter portion 341 and the large diameter portion342 of the rotary tool 340 are the same. The small diameter portion 341of the rotary tool 340 is in the form of a screw member.

When the respective rotary tools 340 are inserted to a predetermineddepth into the surface of the respective hollow-extruded members, themovement of the gantry 320, which carries plural friction stir weldingapparatuses 330, is started to carry the welding apparatuses toward theother end, so that friction stir welding is carried out.

Next, the operation of the friction stir welding apparatus 330 in thevicinity of the window 210 and the inlet and outlet port 220 will beexplained with reference to FIG. 1 and FIG. 2. Herein, the formation ofthe window 210 will be considered by way of example. The rotary tool 340which operates on the welding line intercepted by the window 210 isindicated as “340A” and the rotary tools 340 which operate on thewelding lines not intercepted by the window 210 are indicated as “340B”.The rotary tools 340A and 340B are inserted at the same time and movefrom left to the right as shown in FIG. 1.

When the friction stir welding has advanced from the end portion of theextruded frame member to a point where the rotary tools 340A and 340Breach the position P1 of the extending portions 28 and 38 at the window210, while continuing the rotation of the rotary tool 340A, the rotarytool 340A is withdrawn from the welding joint. Namely, the rotary tool340A is raised, but the forward movement is continued. For this purpose,the rotary tool 340A is raised gradually. The position P1 is determinedby the running distance (position) of the gantry 320. The position P1 isdetermined in advance. (step S10 and step S30).

After the friction stir welding is completed, the extending portions 28and 38 will be cut off in line with the edge of the window opening. Forthis reason, since the extending portions 28 and 38 are positioned at anupstream side of the position P1, there is no problem about the weldingdepth from the strength aspect of the remaining welded portion. Therotary tools 340B are not raised at the position P1 since the window 210does not interrupt the welding lines associated therewith. The rotarytools 340B continue to move along their respective welding lines and thefriction stir welding performed thereby is continued beyond the positionP1.

As stated above, since the rotary tool 340A is raised while the forwardmovement thereof continues, without stopping the welding being carriedout by the rotary tools 340A and 340B, the welding time can beshortened.

When the rotary tool 340A reaches the predetermined position (a positionP2), the raising of the rotary tool 340A and the rotation thereof arestopped. At this point, the rotary tool 340A has been elevatedsufficiently that it is carried at a level about the surface of theraised portions 25 and 35. When the small diameter 341 of the rotarytool 340A has been pulled entirely out (withdrawn) of the raisedportions 25 and 35, the friction stir welding is stopped along thewelding line.

When the rotary tools 340A and 340B reach the other end of the window210, namely to a predetermined position P3, which is this side of theextending portions 29 and 39, a raising (withdrawal) of the rotary tools340B starts. The speed of withdrawal of the rotary tools 340B from therespective welding joint is slow, while the movement of the gantry 320continues. For this reason, the welding depth at which the rotary tools340B operate become gradually more shallow. (step S50 and step S70).

When the rotary tool 340A reaches the position P4 at the extendingportions 29 and 39, the movement of the gantry 320 is stopped. At thistime, since the raising of the rotary tools 340B is continued, theserotary tools 340B are pulled completely out of the respective weldingjoints. At the position P4, the speed of withdrawal of the rotary tools340B may be increased. The position P4 is located on the other side ofthe temporary welding position W. (step 90 and step 110).

The distance between the position P3 and the position P4 is, forexample, 50 mm. The amount that the rotary tool 340B is withdrawnbetween the position P3 and the position P4 is, for example, 0.5 mm.With this amount of withdrawal, the welding depth becomes small in theremainder of the extending portions 28, 38. With this minimum weldingdepth, no problem occurs from the aspect of the strength of the weldedportion.

When the rotary tool 340B is pulled out, in the welded portion a holewhich corresponds to the diameter of the small diameter portion 341 ofthe rotary tool 340 is formed.

Next, at the position P4, all rotary tools 340A and 340B are made torotate and descend, and the rotary tool 340A and the rotary tools 340Bare inserted into the welding joints to a predetermined depth. Theinsertion amounts of the rotary tools 340A and 340B are the regular(stationary) depth. (step S130).

The rotary tools 340B are inserted into the above-stated holes. Sincethe insertion amount of the rotary tool 340B is the regular depth, theinsertion depth is the same as it was before the position P3 (theinsertion depth before the starting of the raising of the rotary tool340B). Namely, at the position P4, the depth is the same as it wasbefore the friction stir welding was stopped and plus 0.5 mm. With this,from the lowest end portion of the above-stated hole which was generatedjust before the rotary tool 340B was pulled out, the rotary tool isinserted deeply with an additional 0.5 mm.

In this condition, the movement of the gantry 320 begins to start. Usingthe rotary tools 340A and 340B, the friction stir welding is startedagain. In this way, friction stir welding to the regular depth iscarried out (step S150).

As stated above, in the position P4, by inserting the rotary tools 340Binto the holes which are formed prior to the pulling out of the rotarytools 340B, the friction stir welding is carried out. For this reason,the hole is buried with metal derived from the raised portions 25 and 35as the welding proceeds. Further, since the position of the lower end ofthe rotary tool 340B is lower than the lowest end of the above-statedhole, and since the lower portion of the above-stated hole is joinedfully, the occurrence of a defect at this portion can be restrained. Inparticular, since by the rotary tool 340B the lower portion at thebottom of the above-stated hole is stirred fully, a defect at the centerportion of the bottom of the above stated hole can be avoided.

Further, even if a defect occurs at the central portion of the bottom ofthe above-stated hole, the size of the defect will not be large, andfrom the aspect of the strength of the weld, a full joining can beobtained.

Since the insertion position of the rotary tool 240A is located at theother side of the temporary welding position W of the end of theextending portions 29 and 39, the gap between the extending portions 29and 39, which forms the welding joint, is not enlarged. Accordingly, agood welding can be carried out.

The next window 210 is carried out in a similar way. Also, the raisingand lowering of the rotary tool 340 at the inlet and outlet port 220 iscarried out in a similar way. Further, it is not necessary for allrotary tools 340 to be arranged on the same line.

As stated above, the welding is carried out to the other end, and thenthe structural body comprised of the plural hollow frame members isturned over on the bed 310 and the friction stir welding is carried outin a similar way. The raised portions at the outer face side of the carbody are cut off and the outer face thereof is made to have the samesmooth face as that of the face plate.

Further, the following processing will be carried out. In a case where adefect is not prevented with the above-stated insertion depth at theposition P4, the rotary tool 340 is inserted even more deeply at thisposition and the welding portion is made thick. As a result, after thestart of movement of the rotary tools, at the position P5 (or after apredetermined time lapses), it is possible to carry out the raising ofthe rotary tool 340B. Accordingly, the insertion depth becomes regular.

This ascent of the rotary tool 340B is carried out by a height positioncontrol function of the rotary tool 340. The height position controlfunction of the rotary tool 340 is a function in which the height of theraised portions 25 and 35 is detected by the sensor, and the insertionamount from the raised portions 25 and 35 is given a predeterminedvalue. With this, all rotary tools 340A and 340B are made to operate ina regular condition.

Further, the following processing will be carried out. Up to theposition P4 the friction stir welding is carried out with the regularinsertion depth, and at the position P4, the rotary tool 340B is pulledout. Next, at the position P4, the rotary tools 340A and 340B areinserted once again into the respective welding joints. The insertiondepth of the rotary tool 340A is the regular amount. The insertionamount of the rotary tool 340B is larger than that of the regularamount; for example, it is plus 0.5 mm. At this time, the movement (therunning) of the rotary tools 340A and 340B will start. After the ofstart movement, at the position P5 (or after the predetermined timeslapses), the raising of the rotary tool 340B starts. The of speedwithdrawal of the rotary tool 340B is slow, while the movement of thegantry 320 continues. For this reason, the welding depth of the rotarytool 340B becomes gradually more shallow.

When the rotary tool 340B is withdrawn to the predetermined position(the insertion depth before the position P4), the withdrawal of therotary tool 340B is stopped. Accordingly, all rotary tools 340A and 340Bare in a regular condition. Further, the positions P1, P2, P3 and P4 canbe managed according to the time.

At the position where the rotary tool 340B are pulled out and then therotary tools 340 can not be inserted immediately for some reason, aftermovement of the gantry 320 is started, at the position P4, the rotarytools 340A and 340B can be inserted into the respective welding joints.

Further, at the position P4 where the rotary tools 340B are pulled out,rather than insert the rotary tools 340B into the hole which is formedby pulling the rotary tool 340B out, it is possible to insert the rotarytool 340B at a position upstream of the position P4. In this case, theinsertion amount during the second insertion of the rotary tool 340Awill be the same as the insertion amount during the case in which theformer welding is carried out.

Now, another embodiment of a method of manufacture of a structural bodyaccording to the present invention will be explained with reference toFIG. 6. When the rotary tool 340A and the rotary tool 340B reach theother end of the window 210, namely the rotary tools 340A and 340B reachthe extending portions 29 and 39, the rotary tool 340A is lowered whileit is rotating and then the rotary tool 340A is inserted into thewelding joint to a predetermined depth. The insertion position P4, wherethe rotary tool 340A is inserted into the extending portions 29 and 39is on the other side (a downstream side) of the temporary weldingposition W.

Since the rotary tool 340A is lowered while it is moved along thewelding line, the welding depth becomes deep gradually. When theinsertion amount of the rotary tool 340A reaches a predetermined amount,the lowering of the rotary tool 340A is stopped (at position P5).Accordingly, friction stir welding at a regular depth is carried out.

The position P5 where the insertion amount of the rotary tool 340Abecomes regular is on the extending portions 29 and 39 before reachingthe edge of the window opening. After the welding is complete, theextending portions 29 and 39 are cut off. The insertion amount of therotary tool 340A is controlled according to the output of an opticalsensor.

As stated above, since the rotary tool 340A is lowered while moving therotary tool 340A along the welding line, without stopping the movementof either the rotary tool 340A or the rotary tools 340B, to cause therotary tool 340A to be inserted into the welding joint between thehollow frame members 20 and 30, the time for welding can be shortened.

Since the insertion position of the rotary tool 340A is located on theother side of the temporary welding position W on the extending portions29 and 39, and welding commences prior to the cut-off of the temporarywelding portion, the gap between the extending portions 29 and 39, whichforms the welding joint, is not enlarged. For this reason, a goodwelding can be carried out.

The gap between the two members at the insertion position (the beginningend of the welding line) of the rotary tool 340 may enlarge easily,however not only are the upper faces of the raised portions 25 and 35temporarily welded, but also temporary welding is carried out on the endformed by the extending portions 29 and 39 in a thickness direction.Accordingly, the extruding portions 29 and 39 at the extreme end can beheld together strongly. Thus, the enlargement of the beginning end ofthe welding line can be prevented easily.

Further, at the end portions of the hollow frame members 20 and 30,namely at the first insertion position of the rotary tools 340A and340B, the extending portions 29 and 39 are provided, and the temporarywelding portion W and the insertion position of the rotary tools 340Aand 340B are formed in a manner similar to that of the formerembodiment. Accordingly, in comparison with the case of temporarilywelding only the upper face of the hollow frame members, the length ofthe chip can be shortened. Accordingly, the length of the hollow framemember can be shortened.

The technical range according to the present invention is not limited tothe description of each embodiment defined in the claims items and thewordings of the description of the items for solving the problem and itcan refer to the range in which the ordinary man belonged to thistechnical field can replace easily.

According to a first feature of the present invention, in the case wherethe welding of plural lines is to be carried out at the same time usingfriction stir welding, and where there is a portion along the weldingline where the members to be subjected to the welding not exist andwhere friction stir welding is unnecessary, when the interrupted weldingis started again, a good friction stir welding can be obtained.

According to the second feature of the present invention, in the casewhere the welding of plural lines is to be carried out at the same timeusing friction stir welding, and where a portion exists along thewelding line where the members to be subjected to welding do not existand in which friction stir welding is unnecessary, when the interruptedwelding is started again, the welding can be carried out in a shorttime.

What is claimed is:
 1. A method of manufacturing a structural body,comprising the steps of: abutting two members; temporarily welding abeginning end of a joining line of an abutted portion of said twomembers to form a welded position; at a finishing end side of saidwelded position, starting the friction stir welding by inserting arotary tool.
 2. A manufacturing method according to claim 1, whereinsaid member is a hollow frame member, and said rotary tool is insertedat a portion of said abutted portion having a seat for supporting a faceplate of an opposite part of said hollow frame member.
 3. A method ofmanufacturing a structural body, comprising the steps of: mounting twomembers on an arc shaped bed and abutting said two members against eachother; temporarily welding a beginning end of a joining line of anabutted portion of said two members to form a welded position; at afinishing end side of said welded position, starting the friction stirwelding by inserting a rotary tool.